Hollow core optical fibers and methods of making

Abstract

A method of manufacturing a preform, the method including positioning at least one glass tube in a glass outer cladding to form a preform precursor, the glass tube comprising a first open end and a second open end, forming a preform from the preform precursor, and thermally treating at least one of the preform precursor and the preform. The thermally treating including sealing the first open end and the second open end of the glass tube to form a closed tube and heating and/or cooling the glass tube to manipulate gas pressure within the closed glass tube.

What is claimed is: 
     
         1 . A method of manufacturing a preform, the method comprising:
 positioning at least one glass tube in a glass outer cladding to form a preform precursor, the glass tube comprising a first open end and a second open end;   forming a preform from the preform precursor; and   thermally treating at least one of the preform precursor and the preform, the thermally treating comprising:
 sealing the first open end and the second open end of the glass tube to form a closed tube; and 
 heating and/or cooling the glass tube to manipulate gas pressure within the closed glass tube. 
   
     
     
         2 . The method of  claim 1 , wherein the thermally treating the glass tube comprises heating the glass tube to a temperature from about 1100° C. to about 2200° C. 
     
     
         3 . The method of  claim 2 , wherein the thermally treating the glass tube comprises heating the glass tube to a temperature from about 1100° C. to about 1700° C. 
     
     
         4 . The method of  claim 1 , wherein the thermally treating the glass tube comprises cooling the glass tube to a temperature from about 0° C. or lower. 
     
     
         5 . The method of  claim 1 , further comprising consolidating the preform precursor to form the preform, and wherein the thermally treating the glass tube is before depositing soot on the preform precursor during the consolidation of the preform precursor. 
     
     
         6 . The method of  claim 1 , further comprising thermally treating a second glass tube, the second glass tube being a nested tube disposed radially interior of the glass tube. 
     
     
         7 . The method of  claim 6 , wherein during the thermal treatment of the glass tube and the thermal treatment of the second glass tube, the glass tube is heated to a different temperature than the second glass tube. 
     
     
         8 . The method of  claim 1 , wherein the thermally treating the glass tube comprises heating gas in a radially central portion of the glass tube to a higher temperature than gas at a radially peripheral portion of the glass tube. 
     
     
         9 . The method of  claim 1 , further comprising consolidating the preform precursor to form the preform, and wherein the thermally treating the glass tube is after depositing soot on the preform precursor during the consolidation of the preform precursor. 
     
     
         10 . The method of  claim 9 , wherein the glass tube that experiences the thermal treatment is a glass tube of the preform. 
     
     
         11 . The method of  claim 9 , further comprising redrawing the preform before drawing the preform and after the thermally treating the glass tube. 
     
     
         12 . The method of  claim 11 , wherein a ratio between a wall thickness of the glass tube before the redraw to after the redraw is about 1.5 or more. 
     
     
         13 . The method of  claim 11 , wherein an outer diameter of the glass tube after the redrawing of the glass tube is from about 0.25 mm to about 10 mm. 
     
     
         14 . The method of  claim 13 , wherein the outer diameter is from about 0.50 mm to about 8 mm. 
     
     
         15 . The method of  claim 1 , wherein the thermally treating the glass tube comprises heating the glass tube and increasing gas pressure within the glass tube. 
     
     
         16 . The method of  claim 15 , wherein the glass tube comprises an inner capillary, and heating the glass tube increases an outer diameter of the inner capillary and decreases a wall thickness of the glass tube. 
     
     
         17 . The method of  claim 1 , wherein the thermally treating the glass tube comprises cooling the glass tube and decreasing gas pressure within the glass tube. 
     
     
         18 . The method of  claim 17 , wherein the glass tube comprises an inner capillary, and cooling the glass tube decreases an outer diameter of the inner capillary and increases a wall thickness of the glass tube. 
     
     
         19 . The method of  claim 1 , wherein the at least one glass tube comprises a second glass tube, the thermally treating the glass tube comprising heating the glass tube to increase a gas pressure within the glass tube, and the method further comprising cooling the second glass tube and sealing both ends of the second glass tube to form a second closed tube to decrease a gas pressure within the second glass tube. 
     
     
         20 . The method of  claim 1 , wherein the at least one glass tube comprises a second glass tube, the thermally treating the glass tube comprising heating the glass tube to a first temperature to increase a gas pressure within the glass tube, and the method further comprising sealing both ends of the second glass tube to form a second closed tube and heating the second glass tube to a second temperature to increase a gas pressure within the second glass tube.